[en] This thesis presents a search for physics beyond the Standard Model with jets, missing transverse momentum, and a single tau. It aims especially at a cosmological favored region in Supersymmetry, the stau-LSP co-annihilation region with an enhanced production of taus. It is performed with data taken 2011 by the CMS experiment at the LHC, corresponding to an integrated luminosity of 5 fb^-1. The background was divided in two different contributions, one with real and one with fake taus. Both estimates were derived with data-driven techniques. The final measurement yields 28 events, while the number of background events was predicted to be 28.5 ± 2.6 (stat) ± 2.4 (syst), and thus, no deviation from the Standard Model could be found. As a result, exclusion limits on the supersymmetric cMSSM have been calculated. Data taking and distribution imposes a challenge to the computing grid. To monitor the stability of the infrastructure, modules for Tier 2 operations within the HappyFace Project have been developed, tested, and taken into usage.